No need to send in your books to have them bound- 'Slip-on" cover with grey polyurethane material that matches the 2013 NWT Bible and can be personalized. Choose between Poly Grey and Poly Grey Plus. Both materials are made of polyurethane by the same manufacturer. The Poly Grey is the exact match to 2013 revised NWT. The Poly Grey Plus is slightly lighter in color but more durable finish that can be cleaned with household cleaners to take off ink stains, etc. Polyurethane is not as durable as leather but we must charge same price as leather because more labor is involved.Watch video below to see difference between Poly and Poly Plus.